As used herein, a wireless transmit/receive unit (WTRU) includes, but is not limited to, a user equipment, mobile station fixed or mobile subscriber unit, pager, or any other type of device capable of operating in a wireless environment. When referred to hereafter, a base station includes, but is not limited to, a base station, Node B, site controller, access point, or other interfacing device in a wireless environment.
In wireless communications, one of the most important features in maintaining the communication link quality under fading and interference situations is power control. In third generation partnership program (3GPP) wideband code division multiple access (W-CDMA) systems utilizing time division duplex (TDD) mode, the UTRAN (SRNC-RRC) sets the initial target signal to interference ratio (SIR) to the WTRU at the call/session establishment and then subsequently continuously adjusts the target SIR of the WTRU during the life term of the call as dictated by the observation of the uplink (UL) block error rate (BLER) measurement.
A variety of services, such as video, voice, and data, each having different Quality of Service (QoS) requirements, can be transmitted using a single wireless connection. This is accomplished by multiplexing several transport channels (TrCHs), each service on its own TrCH, onto a coded composite transport channel (CCTrCH). The transmitted information is sent in units of transport blocks (TBs). Each service's QoS requirement can be monitored on a BLER basis. The rate at which each service is transmitted is on a transmission time interval (TTI). The smallest interval is one frame of data, typically defined as 10 ms for a 3 G communication system. Each frame is tracked by a system connection frame number (CFN), which is encoded into the frame header. TTIs are typically in intervals of 10 ms frame durations (i.e., 10, 20, 30, 40 ms, etc.). In particular for 3GPP systems, TTIs can only be 10, 20, 40, or 80 ms. The TTI for each service depends on the type of service and its QoS requirements. Because of these differences, a variety of TTIs associated with their respective TrCHs may exist on a single CCTrCH.
In order to monitor the BLER value at a CCTrCH level, as opposed to a TrCH level, one approach is to simultaneously monitor the BLER value of each TrCH multiplexed on the CCTrCH. A drawback to this approach is the potentially excessive use of system resources to monitor more channels than may be necessary.
Alternatively, in order to monitor the BLER level on a CCTrCH basis, a reference transport channel (RTrCH) may be selected among the transport channels multiplexed on the considered CCTrCH. The difficulty of this approach, especially for variable bit rate services, is the reselection of the RTrCH, since the initially selected RTrCH may become temporarily unavailable (OFF) during periods where it does not carry any data.